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Friday, May 09, 2008

Now, gum swab to spot HIV

A simple gum swab in place of an invasive blood test can now tell whether you are HIV positive. What's even better, the test results will be out in just 10-20 minutes. In a breakthrough that could replace the present day HIV antibody test through blood taken from the finger or the arm, a team of Indo-Canadian scientists has successfully tested the world's first saliva-based HIV test, with an accuracy rate of nearly 100%. The final results from the study, conducted in Maharashtra in 2006, by a team from McGill University Health Centre (MUHC), Canada, and Mahatma Gandhi Institute of Medical Sciences (MGIMS), Sevagram, were published on Tuesday in the international medical journal ‘PloS Medicine'. This test is based on oral mucosal transudate (OMT), a fluid that is secreted at the base of the gums before it becomes saliva. Scientists found that the level of antibodies in OMT is comparable to that of blood plasma, making it an excellent sample for HIV testing. Lead author Nitika Pant Pai from MUHC's division of infectious diseases, said this new technique would do away with blood collection, which scares away patients from undergoing HIV test. The team now hopes that this research will pave the way for widespread use of oral HIV tests available over-the-counter. Rai conducted clinical trials on vulnerable pregnant women in the labour ward of MGIMS. She said that extracting blood in field settings poses a logistical problem because it needs injecting syringes and trained personnel. Now, all that one has to do is rub the stick against the gum twice to collect oral fluid. "The applicator on the stick, a strip of synthetic proteins, then detects HIV antibodies in 20 minutes or less. Standard blood test for HIV takes up to two weeks," Dr Pai said. She added that in India, it is vital to determine the HIV status of mothers very quickly to prevent transmission to the child during delivery. "Over 50% Indian women do not receive prenatal care and therefore don't get tested for HIV during pregnancy. Testing in the labour ward is the last chance to prevent HIV transmission to the newborn baby. Also Indian patients often refuse blood collection in fear of social ostracization, while saliva collection poses no problem. Thanks to this test, women were enrolled, received counselling, their test results confirmed and referred for treatment when found positive, within 40-60 minutes," she said. Globally, in 2007, about 2.1 million children were detected with new HIV infection - 90% of them having acquired it via maternal fetal transmission. Without rapid and accurate detection of HIV, no delivery of available PMTCT interventions (prevention of mother to child HIV transmission) is possible. Without anti-retroviral drugs, the probability of transmission is 30-35%. With ART, it is reduced to 10-15%. "In the labour room, due to inconsistent supply of blood-based rapid tests, they are often not available. Thus, many fail to get tested. In India, 4,755 infants were detected in 2005 attributed to mother-to-child transmission," Pai added.